Sutures are generally coated with a lubricious coating to improve the tie down and knot adjustability of the suture. Additionally, these coatings may also reduce the drag associated with passing the suture through the tissue thereby reducing the tissue trauma.
The coatings that are applied to sutures generally contain a biocompatable polymer and optionally other additives such as, fatty acid salts or esters may be added into the coating to further improve the lubricity of the coated sutures. These coatings are usually dissolved or suspended in a volatile organic liquid and applied in the form of a liquid coating to the sutures. Conventionally these liquid coatings have been applied by dip coating, bushing, wiping, drip coating, spray coating or by using a coating/filling head. Sutures can be dip coated in a batch process by winding a suture on a frame and immersing the frame into a coating solution or in a continuous process in which the suture is passed under tension into a dip tank then through a drying tunnel (as described in U.S. Pat. No. 3,982,543). In a continuous dip coating process sutures are generally coated at a rate of about 45-60 feet per minute. Another means of coating sutures is to drip coat a suture using a syringe pump to apply the coating to a moving suture. Sutures can be drip coated at about 44 meters per minute, (described in U.S. Pat. No. 5,472,702 column 7, lines 1-20). Coating/filling heads have also been used to coat sutures, such as the filling heads described in U.S. Pat. No. 5,447,100. The speed at which sutures are coated using these filling heads is about 50 meters per minute (see column 14, line 58 of U.S. Pat. 5,447,100).
Although the coating process that have been conventionally used provide acceptable coatings for sutures, the production speeds at which the coatings are applied are very low. Therefore, it would be a significant contribution to the art of suture production to provide a faster means for coating sutures.